The subject of the present invention is a device which permits batteries, in particular battery button cells, to be introduced into an X-ray beam, synchrotron beam or other probe beam, in order to carry out diffractometric or spectroscopic examination on these batteries during charging or respectively discharging.
Within the development of high-performance batteries, in particular of accumulators, it is of particularly great interest to examine the structural chemical processes which occur during the charging and discharging of the battery system. Such examinations are designated as in situ examinations. In this context, in situ means in particular: the quantitative examination of the crystalline structure, the electrode morphology or the surface chemistry of all components which are involved, whilst the battery is continuously charged and discharged (i.e. without interruption of the current supply).
Examinations by means of X-ray or respectively synchrotron radiation are particularly beneficial and widely-used, because the wavelength thereof lies in the scale range of the atomic structure. This permits a quantitative examination of structural chemical phenomena and a detailed description, for example of phase fractions, lattice parameters or atom positions as a function of the charging status of the battery material. Synchrotron radiation offers extreme temporal and instrumental resolutions and is therefore used most frequently. The housings of the batteries which are to be examined generally have openings for beam entry or respectively beam exit, for the examination. These openings can also be covered by materials which only interact slightly with the radiation which is used.
Radiographic and reflection diffractometry come into use here in particular as methods. The so-called in situ PDF (pair distribution function) methods or fluorescence analysis, in particular absorption spectroscopy are also increasingly carried out.
Whereas in radiographic diffractometry and absorption spectroscopy the diffraction- or respectively absorption pattern, occurring behind the object which is to be examined, is analysed, reflection diffractometry is a method in which both the radiation source and also the detector are arranged above the same surface. The beam diameters of the X-ray or synchrotron radiation are generally less than 3 mm and are mostly even below this (approximately 1 mm).
The radiation time, therefore the time which is available for the diffractometric measurements, is generally small and, in particular in the case of the use of synchrotron radiation, is also particularly expensive. The time available is therefore to be utilized effectively. It is therefore aimed to use as little time as possible for the placing and adjusting of the sample (battery) in the path of rays and to measure as many samples as possible simultaneously (i.e. sequentially). For this purpose, special sample mountings have been developed.
U.S. Pat. No. 5,127,039 describes a sample holder for X-ray diffractometry. A particular characteristic of this development is the adjustability in every spatial direction. The device is also to have a sample holder. The latter is configured rotatably, so that it can rotate during the irradiation. However, provision is not made to insert several samples. The rotational movement refers here only to an individual sample, even if mention is made of a “sample disc” (column 3, II. 1-8). The rotation axis of the sample holder is perpendicular here to the beam axis and intersects the latter. A refitting for measuring the next sample is still time-consuming here, however.
The subject of US 2014/0106216 A1 is a method for subjecting layers, from which a lithium-ion battery is constructed, to a local heat treatment during manufacture. During the manufacturing process, sputtering processes take place, for which the use of a sample holder carousel is proposed. A direct transferability to diffractometric examination does not exist.
US 2014/0093052 A1 proposes a test chamber for X-ray or neutron spectroscopy on batteries and fuel cells. The subjects of the examination do not bring their own housings here, but rather are assembled in the sample chambers of the test chamber. The test chamber is embodied as a two-part housing with an upper part and a lower part. The contacting of the cells takes place via feedthroughs through which the contact lines lead to the battery wall or respectively to the cover of the battery. A disadvantage in this construction is that the contacting of the battery takes place via lines which can not guarantee a reliable making of contact. In particular, the test chamber is therefore only suitable for one single battery size.
U.S. Pat. No. 7,022,290 B2 describes a hermetically sealed examination chamber for batteries. The examination chamber consists of a base body with an insertion opening for the battery and a cover which has an opening for the beam entry. This construction is suitable exclusively for back radiation examinations, because there is no possibility for detecting a beam passing through the battery, because there is no suitable outlet opening.
In WO 96/22523 a device is proposed for the examination of batteries by means of X-radiation. The device consists of an upper part and a lower part, which are electrically insulated from one another. The contacting of the battery takes place via connections on this upper or respectively lower part, whilst the battery is clamped between these parts. The underside of the battery is contacted through a copper block, whilst the upper part is exposed to the radiation via a window. This device is likewise not suitable for radiographic examinations, because the copper block would falsify the measurement results.
In JP 2012-159311 A a device is described which is intended to receive the individual layers of a battery and to make them accessible for examination. Here, the layers of the battery are clamped between two counter-pieces, which have windows for beam entry or respectively exit. This device concerns a solution for handling an individual cell. The positioning in the beam takes place via a special holder for receiving the device. A quick changeover of samples and a reliable voltage supply are thus not guaranteed.
The subject of JP 10-054809 A is a device consisting of an upper part and a lower part, which are electrically insulated with respect to one another. Clamped between these parts is the layer stack of a battery with electrolyte. The contacting takes place via the upper or respectively lower part. The two parts have windows for passage of the beam. The device is not suitable to receive prefabricated battery bodies and to deliver these for a quick measurement. Rather, the device itself is to be regarded as a battery housing for experimental layerings and electrolytes of batteries.
The company Anton Paar (http://www.anton-paar.com/?eID=documentsDownload&document=2065&L=8, webpage status: 18 Jun. 2014) proposes a sample support which has a sample wheel. This is to be situated in a microclimate chamber and the possibility exists to move one of eight samples into an X-ray beam. A radiography of the sample is provided. The sample wheel is aligned substantially horizontally. The sample supports are not able to be closed, so that a change in the position of the sample wheel is not readily possible. Moreover, no individual deliveries of media or of electrical energy are provided to the individual samples. In situ battery examinations are therefore not able to be carried out.
In the article “Advances in in situ powder diffraction of battery materials: a case study of the new beam line P02.1 at DESY, Hamburg”, M. Herklotz et al. Journal of Applied Crystallography, (2013). 46. P. 1117-1127 a sample support is shown, which has four battery holders which are arranged around the centre point of the circular sample support. The sample support is also embodied so as to be rotatable about this centre point. Each of the battery holders can be electrically connected, so that in situ measurements are possible. A problem is that the current supply takes place via several cables (2 per battery), which lead in an undefined manner away from the side of the sample support facing the primary beam. It can happen here that during the measuring process or on a rotation of the sample support, cables arrive into the path of rays and lead to a falsification of the measurement results. Furthermore, through the fixing of the sample cover by means of screws, the changeover of samples is laborious, time-consuming and susceptible to error.